Fracture fixation plate and method of manufacturing

Abstract

The present disclosure provides a method of manufacturing a fracture fixation plate for stabilising a bone fracture. The method comprises inserting a charge into a cavity of a compression moulding tool and applying pressure to the charge within the cavity to alter a shape of the charge to form a fracture fixation plate precursor. The cavity of the compression moulding tool is shaped to mould: (a) one or more edge features of the fracture fixation plate; and (b) a lip which projects outward beyond the one or more edge features and extends at least partially around a perimeter of the fracture fixation plate precursor. The method further includes removing the lip from the fracture fixation plate precursor to form the fracture fixation plate.

Description

FRACTURE FIXATION PLATE

[0001] The present disclosure relates to a fracture fixation plate, and in particular to a method of manufacturing a fracture fixation plate, a fracture fixation plate precursor, a fracture fixation plate, and a compression moulding tool for manufacturing a fracture fixation plate precursor.BACKGROUND

[0002] Fracture fixation plates (also known as bone plates or trauma plates) may be used in surgery to fix bone fragments together and to realign bones and bone fragments. Fracture fixation plates typically include pre-formed screw holes for receiving fixing screws which attach the plate to bone.

[0003] Fracture fixation plates have typically been formed of surgical grade stainless steel or titanium. More recently, fracture fixation plates have been formed using fibre- reinforced composite materials, such as carbon-reinforced polyetheretherketone (PEEK). One way to form such composite components is by layering up composite tape layers (or plies) and compressing them together using a compression moulding tool.

[0004] As shown in FIG. 3, typically a compression moulding tool is used to produce an oversized precursor. The precursor is then machined to remove any sharp edges and define the exterior shape of the final fracture fixation plate. The holes are typically machined into the plate in the same process.

[0005] However, post-moulding machining requires a series of precisely controlled passes of a milling bit. This adds complexity and cost to the manufacturing process. The applicant has also appreciated that variation in the thickness of fracture fixation plate precursors (e.g., due to manufacturing tolerances, such as the thicknesses of composite plies) can lead to inconsistency in the final shape of the fracture fixation plate. For example, where a milling tool is used to machine the precursor according to a pre-set pattern (e.g., using a jig), variation in the thickness of the precursor can result in variation in the location and size of the edge features machined into the precursor. In some cases, the machining operation may result in an unintended sharp edge or step extending along an edge of the fracture fixation plate.

[0006] It is an object of the present invention to provide a low cost method of manufacturing fracture fixation plates with improved accuracy and dimensional consistency.BRIEF SUMMARY

[0007] An aspect of the disclosure provides a method of manufacturing a fracture fixation plate for stabilising a bone fracture, comprising inserting a charge into a cavity of a compression moulding tool; applying pressure to the charge within the cavity to alter a shape of the charge to form a fracture fixation plate precursor, wherein the cavity of the compression moulding tool is shaped to mould: one or more edge features of the fracture fixation plate; and a lip which projects outward beyond the one or more edge features and extends at least partially around a perimeter of the fracture fixation plate precursor; and removing the lip from the fracture fixation plate precursor to form the fracture fixation plate.

[0008] The lip may extend fully or partially around the perimeter of the fracture fixation plate precursor. In examples, the fracture fixation plate precursor may comprise more than one lip, for example two lips spaced from each other around the perimeter of the fracture fixation plate precursor.

[0009] The one or more edge features may each extend fully or partially around the perimeter of the fracture fixation plate precursor. The one or more edge features may comprise any one or combination of: a rounded edge; a fillet radius; a chamfered edge, a bevelled edge and a break-edge. The edge features are moulded edge features, whose shape is defined by the compression moulding tool. The edge features may be considered final edge features of the fracture fixation plate. That is, the edge features may not require further cutting, machining, or other processing in order to form their final shape on the fracture fixation plate.

[0010] In contrast, the lip is moulded into the fracture fixation plate precursor and then removed (e.g., by machining) after the moulding process, to form the fracture fixation plate.

[0011] Advantageously, the lip ensures full compression of the charge within the compression moulding tool. That is, during compression moulding the pressure applied to the charge will compress the charge such that it conforms to the shape of the compression moulding tool and is urged into the lip. The lip thereby allows fullcompression with confidence that the cavity of the compression moulding tool is without voids or the like. Additionally, after moulding the lip can be more accurately removed as compared to machining of the edge features. In particular, removing the lip (and not having to machine the edge features) improves the accuracy and repeatability of the finishing operations performed on the fracture fixation plate precursor to form the fracture fixation plate. Therefore, both the compression moulding process and the postmoulding finishing operations are improved by the method of moulding the edge features and the lip in the fracture fixation plate precursor, and then machining only the lip in the post-moulding finishing process. This results in more reliable and dimensionally accurate manufacturing of the fracture fixation plates.

[0012] The fracture fixation plate may comprise an elongate body having a major top surface, a major basal surface, and a side surface that extends between the top surface and the basal surface. The edge features may be provided at a join between the top surface and the side surface, and / or at a join between the basal surface and the side surface.

[0013] The one or more edge features may comprise a top edge feature and a basal edge feature. The lip may be located between the top edge feature and the basal edge feature.

[0014] In one specific example, the top edge feature may comprise a rounded edge and the basal edge feature may comprise a chamfered edge.

[0015] The lip may project outward beyond the top edge feature. The lip may project outward beyond the basal edge feature. The lip may form a skirt or loop extending about the perimeter of the fracture fixation plate precursor.

[0016] The method may include forming one or more holes in the fracture fixation plate for receiving fasteners to couple the fracture fixation plate to the bone. The holes may be formed by any suitable method comprising one or more of: drilling, milling, and / or honing. The holes may be threaded (e.g., tapped).

[0017] The charge may comprise a plurality of plies such as composite plies. The composite plies may comprise carbon fibres.

[0018] There may be variation in the size and / or shape of plies within the plurality of plies. In particular, the charge may comprise:net feature plies sized and shaped to form the one or more moulded edge features; and lip plies which are configured to project into a portion of the cavity that forms the lip.

[0019] In this way, the final edge features of the fracture fixation plate are moulded from the net feature plies, while the lip is formed from excess parts of the lip plies and can be removed post-moulding.

[0020] The cavity of the compression moulding tool may include one or more edge contours for defining the one or more edge features.

[0021] In examples, the compression moulding tool may have at least two tool parts, including a first tool part, having a first contact face for forming a basal surface of the fracture fixation plate for engaging the bone, and a second tool part having a second contact face for forming a top surface of the fracture fixation plate, opposite the basal surface. The first contact face and / or the second contact face may comprise a raised rim to form the one or more edge features. The second contact face may comprise a continuous surface which forms the top surface of the fracture fixation plate. The second contact face may comprise a raised rim which surrounds the continuous surface and forms the top edge feature.

[0022] In examples, the compression moulding tool may be a three part compression moulding tool further including a third tool part having a third contact face which defines a terminal surface of the lip of the fracture fixation plate precursor. The first, second and third contact faces may together define the cavity. When the compression moulding tool is assembled, the third contact face may be contiguous with and extend between the first contact face and the second contact face.

[0023] At least one of the first tool part and the second tool part may comprise a projection on which their respective contact face is disposed. The first tool part may comprise a first projection. The first contact face may be located at a terminal end of the first projection. The second tool part may comprise a second projection. The second contact face may be located at a terminal end of the second projection.

[0024] The third tool part may comprise a through-thickness aperture. The aperture may comprise a first aperture end for receiving first tool part, and a second aperture end for receiving the second tool part. The aperture may be bound by an aperture surfacethat connects the first aperture end to the second aperture end and defines the third contact face.

[0025] The compression moulding tool may comprise one or more overflow channels for receiving excess charge material from the cavity during compression.

[0026] Net feature plies, described above, may be configured (sized, shaped and / or positioned within the mould) to contact the first contact face or the second contact face along a perimeter of the plies.

[0027] The charge may comprise a pre-form of the fracture fixation plate. The charge may comprise a polymer, in particular polyetheretherketone (PEEK). The charge may comprise reinforcement fibres, for example carbon fibres. For example the charge may comprise a series of carbon fibre reinforced plies. The fibres may be arranged in a series of layers (plies) stacked in the thickness direction of the fracture fixation plate.

[0028] In examples, the lip may be removed by hand, by machining (e.g., automated machining (CNC)), or by other suitable processes.

[0029] The method may involve applying pressure and heat to the charge within the cavity of the compression moulding tool to alter a shape of the charge to form a fracture fixation plate precursor. Pressure may be applied to a predetermined maximum pressure value, and / or pressure may be applied until a predetermined position of the compression moulding tool is reached. Applying pressure to the charge within the cavity may comprise compressing the charge in a thickness direction.

[0030] The top edge feature and / or the basal edge feature may be features of the final fracture fixation plate. That is, the top edge feature and the basal edge feature may be moulded to their final shape, not requiring any finishing (machining) after moulding.

[0031] The fracture fixation plate precursor may comprise a basal surface for engaging the bone and a top surface opposite the basal surface.

[0032] The top surface and / or the basal surface may be features of the final fracture fixation plate. That is, the top surface and the basal surface may be moulded to their final shape, not requiring any finishing (machining) after moulding.

[0033] The only machining of the fracture fixation plate precursor required to define an outer geometry of the fracture fixation plate may be the removal of the lip and, optionally, forming the holes.

[0034] In examples, the basal surface is arcuate. In some examples the top surface is arcuate. In use, such an arcuate shape may ensure close contact between the fracture fixation plate and the bone to which it is affixed. Specifically, the basal surface of the fracture fixation plate may be shaped for engaging a bone. The basal surface may be concave. The top surface of the fracture fixation plate may be convex. The curvatures of the top surface and the basal surface may be the same or approximately the same, and the fracture fixation plate may have a substantially uniform thickness, for example uniform thickness.

[0035] In some examples the lip projects substantially parallel to the top surface and / or the basal surface.

[0036] Removing the lip from the fracture fixation plate precursor may from a side surface of the fracture fixation plate. The side surface may be located between the top surface and the basal surface, and in particular between the top edge feature and the basal edge feature. The side surface may extend between the top edge feature and the basal edge feature. In particular, the top edge feature may define a boundary between the top surface and the side surface, and the basal edge feature may define a boundary between the basal surface and the side surface.

[0037] Removing the lip from the fracture fixation plate precursor may consist of machining using a two-axis milling machine. The milling bit may be oriented parallel to a thickness direction of the fracture fixation plate precursor. The side surface formed by the milling may be parallel to the thickness direction of the fracture fixation plate precursor.

[0038] Removing the lip from the fracture fixation plate precursor may consist of machining using a five-axis milling machine. The side surface formed by the milling may be angled with respect to a thickness direction of the fracture fixation plate precursor. For example, the side surface may be angled less than 5 degrees from the thickness direction of the fracture fixation plate precursor.

[0039] Another aspect of the disclosure provides a fracture fixation plate formed according to the method described above.

[0040] Another aspect of the present invention provides a fracture fixation plate precursor of a fracture fixation plate for stabilising a bone fracture, the fracture fixation plate precursor comprising: one or more moulded edge features of the fracture fixationplate; and a lip which projects outward beyond the one or more edge features and extends at least partially around a perimeter of the fracture fixation plate precursor.

[0041] In examples, the lip may extend about the entire perimeter of the fracture fixation plate precursor. In examples, the fracture fixation plate precursor may comprise more than one lip, for example two lips spaced from each other around the perimeter of the fracture fixation plate precursor.

[0042] The one or more edge features may each extend fully or partially around the perimeter of the fracture fixation plate precursor. The one or more edge features may comprise any one or combination of: a rounded edge; a fillet radius; a chamfered edge, a bevelled edge and a break-edge. The edge features are moulded edge features, whose shape is defined by the compression moulding tool. The edge features may be considered final edge features of the fracture fixation plate. That is, the edge features may not require further cutting, machining, or other processing in order to form their final shape on the fracture fixation plate.

[0043] In contrast, the lip, which is a moulded part of the fracture fixation plate precursor, can be removed (e.g., by machining), to form the fracture fixation plate.

[0044] Advantageously, the lip ensures full compression of the material within the compression moulding tool used to form the fracture fixation plate precursor. That is, during compression moulding the pressure applied will compress the material such that it conforms to the shape of the compression moulding tool and is urged into the lip. The lip thereby allows full compression with confidence that the cavity of the compression moulding tool is without voids or the like. Additionally, after moulding the lip can be more accurately removed as compared to machining of the edge features. In particular, removing the lip (and not having to machine the edge features) improves the accuracy and repeatability of the finishing operations performed on the fracture fixation plate precursor to form the fracture fixation plate. Therefore, both the compression moulding process and the post-moulding finishing operations are improved by moulding the edge features and the lip in the fracture fixation plate precursor, and then machining only the lip in the post-moulding finishing process. This results in more reliable and dimensionally accurate manufacturing of the fracture fixation plates.

[0045] The fracture fixation plate precursor may comprise an elongate body having a major top surface, a major basal surface, and a side surface that extends between thetop surface and the basal surface. The lip may be formed on the side surface. The lip may project outwardly from the side surface. The edge features may be provided at a join between the top surface and the side surface, and / or at a join between the basal surface and the side surface.

[0046] In examples, the one or more edge features comprises a top edge feature of the fracture fixation plate precursor and a basal edge feature of the fracture fixation plate precursor, and wherein the lip is located between the top edge feature and the basal edge feature.

[0047] In one specific example, the top edge feature may comprise a rounded edge and the basal edge feature may comprise a chamfered edge.

[0048] The lip may project outward beyond the top edge feature. The lip may project outward beyond the basal edge feature. The lip may form a skirt or loop extending about the perimeter of the fracture fixation plate precursor.

[0049] In examples, the basal surface is arcuate. In some examples the top surface is arcuate. In use, such an arcuate shape may ensure close contact between the fracture fixation plate and the bone to which it is affixed. Specifically, the basal surface of the fracture fixation plate may be shaped for engaging a bone. The basal surface may be concave. The top surface of the fracture fixation plate may be convex. The curvatures of the top surface and the basal surface may be the same or approximately the same, and the fracture fixation plate precursor (and the fracture fixation plate) may have a substantially uniform thickness, for example uniform thickness.

[0050] In some examples the lip projects substantially parallel to the top surface and / or the basal surface.

[0051] The top edge feature and / or the basal edge feature may be features of the final fracture fixation plate. That is, the top edge feature and the basal edge feature may be moulded to their final shape, not requiring any finishing (machining) after moulding.

[0052] The fracture fixation plate precursor may comprise a polymer, in particular polyetheretherketone (PEEK). The fracture fixation plate precursor may comprise reinforcement fibres, in particular carbon fibres. The fibres may be arranged in a series of layers (plies) stacked in a thickness direction of the fracture fixation plate precursor. The layers may extend across a full width and length of the fracture fixation plateprecursor. The fracture fixation plate precursor may comprise a plurality of plies such as composite plies.

[0053] There may be variation in the size and / or shape of plies within the plurality of plies. In particular, the fracture fixation plate precursor may comprise: net feature plies sized and shaped to form the one or more moulded edge features; and lip plies which are configured to project into a portion of the cavity that forms the lip.

[0054] In this way, the final edge features of the fracture fixation plate are moulded into the fracture fixation plate precursor from the net feature plies, while the lip is formed from excess parts of the lip plies and can be removed from the fracture fixation plate precursor to form the final fracture fixation plate.

[0055] According to a further aspect of the present invention there is also provided a fracture fixation plate for stabilising a bone fracture, the fracture fixation plate comprising: one or more moulded edge features; and a machined side surface adjoining the one or more edge features and extending around a perimeter of the fracture fixation plate precursor.

[0056] The one or more edge features may each extend fully or partially around the perimeter of the fracture fixation plate. The one or more edge features may comprise any one or combination of: a rounded edge; a fillet radius; a chamfered edge, a bevelled edge and a break-edge.

[0057] The edge features are moulded edge features. In examples, the shape of the moulded edge features is defined by a compression moulding tool used to form a fracture fixation plate precursor. The edge features are moulded into their final shape, without the need for further cutting, machining, or other processing in order to form their final shape on the fracture fixation plate.

[0058] In contrast, the machined side surface may be formed by machining a moulded fracture fixation plate precursor. For example, a moulded lip or skirt may have been removed from the moulded fracture fixation plate precursor to form the machined side surface of the fracture fixation plate.

[0059] The fracture fixation plate may comprise an elongate body having a major top surface and a major basal surface. The side surface may extend between the top surface and the basal surface. The edge features may be provided at a join betweenthe top surface and the side surface, and / or at a join between the basal surface and the side surface.

[0060] In examples, the one or more edge features comprises a top edge feature of the fracture fixation plate and a basal edge feature of the fracture fixation plate, and wherein the lip is located between the top edge feature and the basal edge feature.

[0061] In one specific example, the top edge feature may comprise a rounded edge and the basal edge feature may comprise a chamfered edge.

[0062] In examples, the basal surface is arcuate. In some examples the top surface is arcuate. In use, such an arcuate shape may ensure close contact between the fracture fixation plate and the bone to which it is affixed. Specifically, the basal surface of the fracture fixation plate may be shaped for engaging a bone. The basal surface may be concave. The top surface of the fracture fixation plate may be convex. The curvatures of the top surface and the basal surface may be the same or approximately the same, and the fracture fixation plate may have a substantially uniform thickness, for example uniform thickness.

[0063] The fracture fixation plate may comprise a polymer, for example polyetheretherketone (PEEK). The fracture fixation plate may comprise reinforcement fibres, such as carbon fibres. The fibres may be arranged in a series of layers (plies) stacked in a thickness direction of the fracture fixation plate. The layers may extend across a full width and length of the fracture fixation plate. The fracture fixation plate may comprise a plurality of plies such as composite plies.

[0064] Another aspect of the disclosure provides a compression moulding tool for forming a fracture fixation plate precursor, comprising at least two tool parts which together form a cavity defining a negative shape of the fracture fixation plate precursor, wherein the cavity of the compression moulding tool is shaped to mould: one or more edge features of the fracture fixation plate; and a lip which projects outward beyond the one or more edge features and extends at least partially around a perimeter of the fracture fixation plate precursor.

[0065] The cavity of the compression moulding tool may include one or more edge contours for defining the one or more edge features. Each of the one or more edge contours may be shaped to impart a respective one of the one or more edge features of the fracture fixation plate.

[0066] The at least two tool parts may comprise a first tool part, having a first contact face for forming a basal surface of the fracture fixation plate for engaging the bone. The at least two tool parts may comprise a second tool part having a second contact face for forming a top surface of the fracture fixation plate, opposite the basal surface.

[0067] The compression moulding tool may be a three part compression moulding tool. The compression moulding tool may further comprise a third tool part having a third contact face which defines a terminal surface of the lip of the fracture fixation plate precursor. The first, second and third contact faces may together define the cavity. When the compression moulding tool is assembled, the third contact face may be contiguous with and extend between the first contact face and the second contact face.

[0068] At least one of the first tool part and the second tool part may comprise a projection on which their respective contact face is disposed. The first tool part may comprise a first projection. The first contact face may be located at a terminal end of the first projection. The second tool part may comprise a second projection. The second contact face may be located at a terminal end of the second projection.

[0069] The third tool part may comprise a through-thickness aperture. The aperture may comprise a first aperture end for receiving the first tool part, in particular the terminal end of the first projection. The aperture may also comprise a second aperture end for receiving the second tool part, in particular the terminal end of the second projection. The aperture may be configured to receive the first projection and second projection at opposing ends of the aperture, i.e. , the first aperture end is opposite the second aperture end. The aperture may be bound by an aperture surface that connects the first aperture end to the second aperture end and defines the third contact face. The aperture surface may connect a top face of the third tool part with a bottom face of the third tool part.

[0070] The compression moulding tool may comprise one or more overflow channels for receiving excess charge material from the cavity during compression.

[0071] The top surface and the bottom surface may be substantially perpendicular to the thickness direction.

[0072] The fibres may be arranged in a series of layers stacked in the thickness direction of the fracture fixation plate. Applying pressure to the charge within the cavity may comprise compressing the charge in a thickness direction.

[0073] The lip may surround the perimeter of the fracture fixation plate precursor to form a skirt or loop. A major axis of the lip may be substantially parallel to the thickness direction of the fracture fixation plate precursor.

[0074] The thickness direction of the precursor may be equivalent to the thickness direction of the fracture fixation plate formed by removing the lip from the fracture fixation plate precursor.

[0075] The lip may be continuous or discontinuous. The lip may extend fully or partially around the edge of the fracture fixation plate precursor.

[0076] The first contact face and / or the second contact face may comprise a raised rim to form the one or more edge features.

[0077] The first contact face may comprise a continuous surface which forms the basal surface of the fracture fixation plate. The first contact face may comprise a raised rim which surrounds the continuous surface and forms the basal edge feature. The second contact face may comprise a continuous surface which forms the top surface of the fracture fixation plate. The second contact face may comprise a raised rim which surrounds the continuous surface and forms the top edge feature.

[0078] The one or more edge features may each extend around the perimeter of the fracture fixation plate precursor. The one or more edge features may comprise any one or combination of: a rounded edge; a fillet radius; a chamfered edge, a bevelled edge and a break-edge. The one or more edge features may comprise a top edge feature and a basal edge feature. The lip may be located between the top edge feature and the basal edge feature.

[0079] In one specific example the top edge feature may comprise a rounded edge and the basal edge feature may comprise a chamfered edge.

[0080] The lip may project outward beyond the top edge feature. The lip may project outward beyond the basal edge feature.

[0081] The top edge feature and / or the basal edge feature may comprise any one of: a rounded edge; a fillet radius; a chamfered edge, a bevelled edge and a break-edge.

[0082] The charge may comprise a plurality of plies, for example composite plies.

[0083] There may be variation in the size and / or shape of plies within the plurality of plies. In particular, the charge may comprise: net feature plies sized and shaped to formthe one or more moulded edge features; and lip plies which are configured to project into a portion of the cavity that forms the lip.

[0084] In this way, the final edge features of the fracture fixation plate are moulded from the net feature plies, while the lip is formed from excess parts of the lip plies and can be removed post-moulding.

[0085] As described above, the fracture fixation plate (and precursor) may comprise a polymer and reinforcement fibres.

[0086] In preferred examples, the polymer of the composite material is a polyaryletherketone. Any suitable polyaryletherketone may be used in the composite material of the present invention. Suitable polyaryletherketone may have repeating units of formula (I) below:Formula (I) where t1 and w1 are independently represent 0 or 1 and v1 represents 0, 1 or 2.

[0087] The polyaryletherketone suitably includes at least 90, 95 or 99 mol % of repeat unit of formula (I).

[0088] The polyaryletherketone may comprise or consist essentially of a repeat unit of formula (I). Preferred polymeric materials comprise (or consist essentially of) a said repeat unit wherein t1 =1 , v1=0 and w1=0; t1 =0, v1 =0 and w1=0; t1 =0, w1 = 1 , v1=2; or t1=0, v1=1 and w1=0. More preferably, the polyaryletherketone comprises (e.g. consists essentially of) the repeat unit I, wherein t1 =1 , v1 =0 and w1 =0; or t1 =0, v1=0 and w1 =0. The most preferred polyaryletherketone comprises (especially consists essentially of) a said repeat unit wherein t1 = 1 , v1=0 and w1=0.

[0089] In preferred embodiments, the polyaryletherketone is selected from polyetheretherketone, polyetherketone, polyetherketoneetherketoneketone and polyetherketoneketone. In a more preferred embodiment, the polyaryletherketone is polyetheretherketone or PEEK.

[0090] The polyaryletherketone (e.g. PEEK) suitably has a melt viscosity (MV) of at least 0.06 kNsm'2, preferably has a MV of at least 0.09 kNsm'2, more preferably at least 0.12 kNsm-2. The polyaryletherketone (e.g. PEEK) may have a MV of less than 1.00 kNsm'2, preferably less than 0.5 kNsm'2.

[0091] The polyaryletherketone (e.g. PEEK) may have a MV in the range 0.09 to 0.5 kNsm'2, preferably in the range 0.1 to 0.3 kNsm'2, preferably having a MV in the range 0.1 to 0.2 kNsm'2. An MV of 0.15 kNsm'2has been found to be particularly advantageous. MV is suitably measured using capillary rheometry operating at 400°C at a shear rate of 1000s-1 using a tungsten carbide die, 0.5mm x 3.175 mm.

[0092] In a preferred embodiment, the polyaryletherketone (e.g. PEEK) has a melt viscosity (MV) of 0.09 kNsm'2to 0.5 kNsm'2.

[0093] The composite material may comprise any suitable amount of the polyaryletherketone (e.g. PEEK). For example, the composite material may comprise at least 20 volume %, preferably at least 25 volume %, more preferably at least 30 volume %, yet more preferably at least 35 volume %, even more preferably at least 37 volume % and most preferably at least 39 volume % polyaryletherketone (e.g. PEEK). The composite material comprises up to 48 volume % polyaryletherketone (e.g. PEEK). In some embodiments, the composite material may comprise up to 45 volume %, up to 43 volume % polyaryletherketone (e.g. PEEK).

[0094] In some embodiments, the composite material may comprise 20 to 48 volume %, preferably 30 to 48 volume %, more preferably 35 to 48 volume %, yet more preferably 37 to 48 volume % or 38 to 48 volume % polyaryletherketone (e.g. PEEK). More preferably, the composite material may comprise 40 to 48 volume %, even more preferably 42 to 45 volume % polyaryletherketone (e.g. PEEK).

[0095] Any suitable reinforcement fibre may be used. The fibres used may be selected from inorganic or organic fibrous materials. The fibres may have a melting or decomposition temperature of greater than 200 °C, for example, greater than 250 °C or greater than 300 °C. In some embodiments, the fibres may have a melting temperature of greater than 350 °C or 500 °C. Examples of suitable fibres include aramid fibres, carbon fibre, glass fibre, silica fibre, zirconia fibre, silicon nitride fibre, boron fibre and potassium titanate fibre. Most preferred fibres are carbon fibres.

[0096] The reinforcement fibre (e.g. carbon fibre) may have a tensile strength of greater than 4,200 MPa, preferably greater than 4,500 MPa, more preferably greater than 4,800 MPa.

[0097] The reinforcement fibre (e.g. carbon fibre) may have a tensile modulus of greater than 200 GPa, preferably greater than 230 GPa, more preferably greater than 240 GPa.

[0098] The reinforcement fibre (e.g. carbon fibre) may have a strain at failure of greater than 1.1 %, preferably, greater than 1.2%, 1.4% or 1.6% The reinforcement fibre (e.g. carbon fibre) may have a strain at failure of less than 2.2%, for instance, less than 2.0% or 1 .9%. In some embodiments, reinforcement fibre (e.g. carbon fibre) may have a strain at failure of 1 .2 to 2.2%, for example, 1 .4 to 2.0 % or 1 .6 to 1 .9%. In one embodiment, the reinforcement fibre (e.g. carbon fibre) may have a strain at failure of 1.7 to 1.9%.

[0099] The reinforcement fibre (e.g. carbon fibre) may have a mass per unit length of 0.1 to 1.0 g / m, for example, 0.2 to 0.8 g / m. In some embodiments, the 0.2 to 0.5 g / m.

[0100] The reinforcement fibre (e.g. carbon fibre) may have a density of greater than 1.65 g / cm3, preferably greater than 1.70 g / cm3. The reinforcement fibre (e.g. carbon fibre) may have a density of less than 1.85 g / cm3, preferably less than 1.80 g / cm3. In some embodiments, the reinforcement fibre (e.g. carbon fibre) may have a density of 1 .70 to 1 .85 g / cm3, for example, 1 .75 to 1 .80 g / cm3, or 1.78 to 1 .79 g / cm3.

[0101] The reinforcement fibre (e.g. carbon fibre) may be provided in the form of a continuous tow. Any suitable tow size may be used. The tow size indicates the number of filaments in the tow. In some embodiments, the tow size may be 1 ,000 to 24,000. In one embodiment, a tow size of 6,000 to 12,000 may be employed.

[0102] Examples of suitable reinforcement fibre include carbon fibres supplied, for example, by Hexcel® under the trademark HexTow®.

[0103] As noted above, the composite material of the present invention comprises polyaryletherketone, and reinforcement fibres.

[0104] The composite material may be formed as a sheet or tape, known as a ply. For example, the reinforcement fibre (e.g. carbon fibre) may be combined with the polyaryletherketone (e.g. PEEK) and formed into a composite ply. The ply may be formed, for example, using heat and / or compression. In an embodiment, the polyaryletherketone (e.g. PEEK) may be heated to above its softening or meltingtemperature to melt or soften the polymer around the fibres to form the composite material. The molten or soften polymer is then compressed around the fibres to form the ply.

[0105] When heat is applied, suitable temperatures include temperatures of 320°C and above, preferably, of 330°C and above, more preferably, of 340°C and above. In some embodiments, compression moulding may be carried out at temperatures of 320 to 450°C, preferably 330 to 400°C, more preferably 340 to 380°C and yet more preferably 350 to 370°C. Suitably, pressures of at least 1 .5 MPa or at least 2 MPa may be applied. Examples of suitable pressures range from 1 .5 to 10 MPa, for instance, 2 to 8 MPa.

[0106] The composite ply formed using the composite material of the present invention may have a thickness of 10 microns to 1 mm, preferably 100 to 300 microns, more preferably 140 to 200 microns.BRIEF DESCRIPTION OF THE DRAWINGS

[0107] Examples of the invention are described with reference to the accompanying drawings, in which:

[0108] FIG. 1 illustrates an example of a fracture fixation plate for stabilising a bone fracture.

[0109] FIG. 2A illustrates an exploded view of a compression moulding tool for manufacturing the fracture fixation plate.

[0110] FIG. 2B illustrates an enlarged cut-out of a portion of FIG. 2A.

[0111] FIG. 3 illustrates a comparison between a fracture fixation plate precursor formed by the compression moulding tool of FIG. 2A and the finished fracture fixation plate after machining.

[0112] FIG. 4 illustrates an exploded view of a compression moulding tool for manufacturing the fracture fixation plate according to the present invention.

[0113] FIG. 5A illustrates a cross-sectional view of the compression moulding tool of FIG. 4 in use.

[0114] FIG. 5B illustrates an enlarged cut-out of a portion of FIG. 5A.

[0115] FIG. 6 illustrates a fracture fixation plate precursor formed by the compression moulding tool of FIG. 4.

[0116] FIG. 7 illustrates a comparison between a fracture fixation plate precursor of FIG. 6 and the finished fracture fixation plate after machining.DETAILED DESCRIPTION

[0117] FIG. 1 illustrates an example of a fracture fixation plate 100 for stabilising a bone fracture. As shown, the fracture fixation plate 100 comprises a plurality of holes 102 for receiving fasteners. In use, fasteners, such as fixing screws, project through the fracture fixation plate 100 and into the bone, coupling the fracture fixation plate 100 to the bone at a series of locations along the bone. In this example, at least some of the holes 102 are threaded to match a corresponding thread of the fixing screws.

[0118] The fracture fixation plate 100 comprises a basal surface 108 for engaging the bone and a top surface 106 opposite the basal surface 108. The fracture fixation plate 100 is elongate and configured to extend substantially parallel to a length of the bone.

[0119] In this example, the fracture fixation plate 100 is shaped to match to an external surface of a bone. The fracture fixation plate 100 is arcuate in shape. In particular, the basal surface 108 is concave to accommodate the curvature of the bone surface around its diameter. In use, such an arcuate shape may ensure close contact between the fracture fixation plate and the bone to which it is affixed.

[0120] The top surface 106 is similarly arced to match the curvature of the bone surface. Beneficially, this may streamline the fracture fixation plate 100 and minimise the total size of implant required.

[0121] As shown in FIG. 1 , the fracture fixation plate 100 has a side surface 110 which extends between the top surface 106 and the basal surface 108. The side surface 110 extends substantially parallel to a thickness 112 of the fracture fixation plate 100.

[0122] Historically, fracture fixation plates have been formed of surgical grade stainless steel or titanium. More recently, fracture fixation plates have been formed of polymers which are sometimes reinforced with fibres to form polymer-fibre composites. The fracture fixation plate 100 may comprise a polymer such as PEEK (polyetheretherketone). In this example, the fracture fixation plate 100 comprises PEEK and reinforcement fibres such as carbon fibres. The fibres are arranged in a series of layers stacked in the thickness direction 112 of the fracture fixation plate 100.

[0123] One way of manufacturing the fracture fixation plates is a multi-stage process which involves compression moulding a charge to form a fracture fixation plate precursor and then machining the precursor to achieve the finished fracture fixation plate. For example, machining the fracture fixation plate precursor may involve drilling and tapping the holes 102 and smoothing the edges of the precursor to remove sharp edges. Chamfers, rounded edges and break-edges were machined into the fracture fixation plate precursor.

[0124] FIG. 2A illustrates an exploded view of a compression moulding tool 200 for manufacturing the fracture fixation plate 100. The compression moulding tool 200 comprises three tool parts: a first tool part 201 , a second tool part 202 and a third tool part 203, which are configured to fit together.

[0125] The first tool part 201 comprises a first contact face 208 shaped to form the basal surface 108. The second tool part 202 comprises a second contact face 209 shaped to form the top surface 106.

[0126] In this example, the first and second tool parts 201 , 202 each comprise a base portion having a projection on which the contact face is disposed. In particular, the first tool part 201 comprises a first base 204 which is substantially planar. The first tool part 201 further comprises a first projection 206 which projects out of and extends orthogonally to first base 204. The first contact face 208 forms a terminal end of the first projection 206. In this example, the first contact face 208 is concave in order to produce the convex shape of the top surface 106.

[0127] Similarly, the second tool part 202 comprises a second base 205 which is substantially planar. The second tool part 202 further comprises a second projection 207 which projects out of and extends orthogonally to the second base 205. The second contact face 209 forms a terminal end of the second projection 207. In this example, the second contact face 209 is convex in order to produce the concave shape of the basal surface 108.

[0128] The third tool part comprises an aperture 210 for receiving the first projection 206 and the second projection 207. The aperture 210 extends through a full thickness of the third tool part 203, between a first aperture end 215 and a second aperture end 216. In use, the terminal end of the first projection 206 is inserted into the first aperture end 215.

[0129] When the first tool part 201 and the third tool part 203 are assembled, a charge such as a plurality of composite plies is placed within the aperture 210 (sat atop the first contact face 208).

[0130] As the desired shape of the fracture fixation plate 100 is curved, the laminar plies which make up the charge are cut to have a larger footprint than the first contact face 208. Each of the plies is bent to conform to the arc of the first contact face 208 as it is inserted into the aperture 210.

[0131] The terminal end of the second projection 207 is then inserted into the second aperture end 216 and the first and second tool parts 202 are compressed together. This compression is best shown in FIG. 2B which illustrates a cross-sectional view of the assembled compression moulding tool 200.

[0132] As shown, the first base 204 and the second base 205 limit the extent to which the first projection 206 and the second projection 207 respectively can extend into the aperture 210. The charge is compressed within a cavity 211 formed between the tool parts 201 , 202, 203. The cavity 211 defines a negative shape of the fracture fixation plate precursor 212.

[0133] During compression, pressure (and optionally heat) is applied to the charge which is compressed between the first tool part 201 and the second tool part 202, as shown by arrows 213.

[0134] Pressure from the opposing first and second tool parts 201 , 202 moulds the charge into the required shape. Where a plurality of composite plies are used as the charge, the plies are bent and solidified into a single arcuate piece (i.e. , fracture fixation plate precursor 212).

[0135] FIG. 2B shows a cross-sectional slice of the fracture fixation plate precursor 212 taken at a midpoint along its length.

[0136] As shown, sharp edges 214 are formed where the tool parts 201 , 202, 203 meet. Such sharp edges may be detrimental to a fracture fixation plate for a variety of reasons. For example, sharp edges in contact with the bone may act as stress concentrators resulting in failure of the implant or the adjacent bone surface. Additionally, sharp edges which face away from the bone surface may cause damage or irritation to overlying tissue. To mitigate these effects, the sharp edges 214 of the fracture fixation plate precursor 212 are removed e.g., by milling. This is best illustratedin FIG. 3 which shows the fracture fixation plate precursor 212 formed by the compression moulding tool 200 alongside the finished fracture fixation plate 100 (post machining).

[0137] The fracture fixation plate precursor 212, as formed by the compression moulding tool 200, is shown on the left hand side of FIG. 3. As shown, the fracture fixation plate precursor 212 has two sharp edges 214 which each extend around a perimeter of the fracture fixation plate precursor 212.

[0138] The fracture fixation plate precursor 212 is machined to produce the fracture fixation plate 100 shown in the center of FIG. 3. During machining, the holes 102 are formed by any suitable process (e.g., by drilling, honing or milling).

[0139] The machining also involves cutting edges features into the fracture fixation plate precursor 212 to remove the sharp edges 214. Cutting edge features may be completed before or after the holes 102 are formed.

[0140] The sharp edges 214 are removed to form a top edge feature 114 and a basal edge feature 116. Typically, a multi-axis milling tool is used to shave off the sharp edges 214. Such tooling allows a precise shape of the edges to be specified according to the design requirements of the application.

[0141] The top edge feature 114 defines a boundary between the top surface 106 and the side surface 110 while the basal edge feature 116 defines a boundary between the basal surface 108 and the side surface 110. In some examples the top edge feature 114 may be a mirror image of the basal edge feature 116 while in other examples the top edge feature and the basal edge feature 116 may differ.

[0142] In this example, the top edge feature 114 is a rounded edge having a continuously curved surface which transitions the top surface 106 into the side surface 110. The basal edge feature 116 is a chamfered edge i.e., a flat surface at an intermediate angle to the side surface 110 and the basal surface 108. It will be understood that various other edge profiles may be used other than the specific examples provided. For example, the top edge feature 114 and / or the basal edge feature 116 may comprise any one of: a rounded edge; a fillet radius; a chamfered edge, a bevelled edge or a break-edge.

[0143] Manufacturing tolerances associated with producing the charge result in variation in its size and shape. In this example where the charge comprises a pluralityof plies, there will be variation in the thickness and cut footprint of the plies. To account for such variation, the cavity 211 is oversized relative to the final fracture fixation plate 100. This ensures that defects such as voids, caused by small variation in the size / shape of the charge, are machined away and do not form part of the final fracture fixation plate 100.

[0144] This is illustrated by the composite image shown on the right hand side of FIG. 3, which illustrates the profile of the fracture fixation plate precursor 212 overlaid onto the profile of the fracture fixation plate 100. As shown, the fracture fixation plate precursor 212 is oversized relative to the desired shape of the final fracture fixation plate 100.

[0145] However, the applicant has appreciated that variation in the thickness of fracture fixation plate precursors can lead to inconsistency in the final shape of the fracture fixation plate. For example, where a milling tool is run according to a pre-set pattern, variation in the thickness of the fracture fixation plate precursors can result in variation in the location and size of the edge features machined into the fracture fixation plate precursor. This effect is not limited to milling and applies to all types of machining as the same jigs are used for are used for each differently sized fracture fixation plate precursor.

[0146] Any variation in the shape or finish of the fracture fixation plates is undesirable due to the exacting performance requirements of fracture fixation plates. For example, variation in the machining of the edge features can be detrimental to the final finish of the fracture fixation plate (e.g., by introducing unwanted sharp edges). In addition, variation can result in machined edge features that are mis-aligned with the profile of the fracture fixation plate.

[0147] As a result, further post-processing may be necessary to improve the finish of the fracture fixation plate. Even still, fracture fixation plates may be scrapped if their measurements deviate too far from the expected values.

[0148] Tailoring the milling pattern according to a measured thickness of each fracture fixation plate precursor is impractical. Such an approach would increase production cost, by adding additional steps to the manufacture process. In addition, such a tailored approach would still fail to account for thickness variation within individual fracture fixation plate precursors.

[0149] It is an object of the present invention to provide a method of manufacturing more consistently shaped fracture fixation plates without increasing the cost of manufacture.

[0150] FIG. 4 illustrates an exploded view of a novel compression moulding tool 300 for manufacturing the fracture fixation plate 100. The compression moulding tool 300 is shaped differently to the compression moulding tool 200 of FIG. 2A and produces a different fracture fixation plate precursor 312.

[0151] The compression moulding tool 300 comprises two or more tool parts 301 , 302, 303 which are configured to fit together. In this example, the compression moulding tool 300 comprises three tool parts: a first tool part 301 , a second tool part 302 and a third tool part 303. In other examples, the compression moulding tool 300 may comprise any number of tool parts for example, 2, 3, 4, 5 or more tool parts.

[0152] The first tool part 301 comprises a first contact face 308 shaped to form the basal surface 108. The second tool part 302 comprises a second contact face 309 shaped to form the top surface 106.

[0153] In this example, the first and second tool parts 301 , 302 each comprise a base portion having a projection on which the contact face is disposed. The first tool part 301 further comprises a first projection 306 which projects out of and extends orthogonally to first base 304. The first contact face 308 forms a terminal end of the first projection 306. In this example, the first contact face 308 is concave in order to produce the convex shape of the top surface 106.

[0154] Similarly, the second tool part 302 comprises a second base 305. The second tool part 302 further comprises a second projection 307 which projects out of and extends orthogonally to the second base 305. The second contact face 309 forms a terminal end of the second projection 307. In this example, the second contact face 309 is convex in order to produce the concave shape of the basal surface 108.

[0155] The third tool part 303 comprises an aperture 310 for receiving the first projection 306 and the second projection 307. The aperture 310 extends through a full thickness of the third tool part 303, between a first aperture end 315 and a second aperture end 316. In use, the terminal end of the first projection 306 is inserted into the first aperture end 315. 1

[0156] In the examples shown, the first base 304 and the second base 305 are both substantially planar and act to limit the extent to which the first projection 306 and the second projection 307 respectively can extend into the aperture 310. The third tool part 303 has flat external surfaces for engaging the first base 304 and the second base 305. It will be understood that these are merely examples and that the external shape of the third tool part 303 as well as the shape of the first base 304 and the second base 305 may differ from the examples shown in the figures. In some examples, the first base 304 and / or the second base 305 may be excluded altogether. In such examples, the relative position of the first tool part 301 with respect to the second tool part 302 may be defined by an external system. For example, the maximum translation of the tool parts 301 , 302 or the maximum compression force may be specified using a controller of a compression control system in which the compression moulding tool 300 is used.

[0157] When the first tool part 301 and the third tool part 303 are assembled, a charge (not shown) is placed within the aperture 310 (i.e., atop the first contact face 308). In other examples, the compression moulding tool 300 may be assembled in a different order. For example, the charge may be placed on the first contact face 308 or the second contact face 309 before the third tool part 303 is assembled with the first tool part 301 or the second tool part 302. In another example, the second tool part 302 and the third tool part 303 may be assembled and then the charge inserted into the aperture 310 (i.e., atop the second contact face 309).

[0158] In this example, the charge (not shown) comprises a plurality of plies. For example, the charge may comprise a polymer such as PEEK. In one example, the charge may comprise a series of fibre reinforced plies (i.e., composite plies containing fibres such as carbon fibres).

[0159] As the desired shape of the fracture fixation plate 100 is curved, the laminar plies which make up the charge are cut to have a larger footprint than the first contact face 308. Each of the plies is bent to conform to the arc of the first contact face 308 as it is inserted into the aperture 310.

[0160] The terminal end of the second projection 307 is then inserted into the second aperture end 316 and the first and second tool parts 302 are compressed together.

[0161] In contrast to the method illustrated in FIG. 1 to FIG. 3, the edge features 114, 116 of the fracture fixation plate 100 are formed in the moulding stage instead of beingformed during post-moulding machining. That is, the top edge features 114, 116 are moulded edge features.

[0162] In order to achieve this, the first and second contact faces 308, 309 are shaped differently to the first and second contact faces 208, 209 of the compression moulding tool 200. For example, the first contact face 308 and the second contact face 309 both include raised rims. In FIG. 4, only the first contact face 308 can be seen as the second contact face 309 is obscured from view.

[0163] As shown, the first contact face 308 comprises a first smooth surface 321 which defines the top surface 106 of the fracture fixation plate 100. The first contact face 308 comprises a first raised rim 318 which extends around a perimeter of the first contact face 308 to completely surround the first smooth surface 321.

[0164] Although not shown in FIG. 4, the second contact face 309 similarly comprises a second smooth surface 322 which defines the basal surface 108 of the fracture fixation plate 100. The second contact face 309 comprises a second raised rim 320 which extends around a perimeter of the second contact face 309 to completely surround the second smooth surface 322. In other examples, the first raised rim 318 and / or the second raised rim 320 may only extend partially around the first contact face 308 and the second contact face 309 respectively.

[0165] The first raised rim 318 is shaped to form the top edge feature 114 into the fracture fixation plate precursor 312. Similarly, the second raised rim 320 is shaped to form the basal edge feature 116 into the fracture fixation plate precursor 312. The effect of the first raised rim 318 and the second raised rim 320 on the resulting fracture fixation plate precursor 312 is best seen in FIG. 5A which illustrates a cross-sectional view of the assembled compression moulding tool 300.

[0166] As shown by arrows 313, during compression moulding the charge is compressed within a cavity 311 formed between the tool parts 301 , 302, 303. The pressure from the opposing first and second tool parts 301 , 302 moulds the charge into the required shape. In this example, where a plurality of composite plies are used as the charge, the plies are bent and solidified into a single arcuate piece to form the fracture fixation plate precursor 312. As such, the cavity 311 defines a negative shape of the fracture fixation plate precursor 312.

[0167] The aperture 310 of the third tool part 303 is bound by an aperture surface 332 that connects the top first aperture end 315 to the second aperture end 316. As shown in FIG. 5A , a section of the aperture surface 332 defines a third contact face 333 which forms part of the cavity 311. As shown, when the compression moulding tool 300 is assembled, the third contact face is contiguous with and extends between the first contact face 308 and the second contact face 309.

[0168] Together, the first contact face 308, the second contact face 309 and the third contact face 333 define the cavity 311 for the charge.

[0169] FIG. 5B shows an enlarged view of a portion of FIG. 5A. As shown, the first raised rim 318 presses into the fracture fixation plate precursor 312 to form the top edge feature 114. In this example, the top edge feature 114 of the fracture fixation plate 100 is a rounded edge. The first raised rim 318 is configured to produce this rounded edge. The first raised rim 318 comprises a top face 324 which is vertically offset relative to the first smooth surface 321.

[0170] The first raised rim 318 further comprises a curved face 326 which connects the first smooth surface 321 to the top face 324 around the perimeter of the first contact face 308. The curve gradually transitions the first smooth surface 321 to the top face 324 of the first raised rim 318. The curved face 326 defines the top edge feature 114 of the fracture fixation plate 100.

[0171] The top face 324 projects outwardly from the curved face 326 towards an exterior of the cavity 311 .

[0172] The second raised rim 320 is positioned opposite the first raised rim 318 and presses into the fracture fixation plate precursor 312 to form the basal edge feature 116. In this example, the basal edge feature 116 of the fracture fixation plate 100 is a chamfered edge. The second raised rim 320 is configured to produce this chamfered edge. The second raised rim 320 comprises a single sloped face 328 which projects at an angle from the second smooth surface 322 (projecting generally outwardly towards the first tool part 301).

[0173] The cavity 311 extends between the first raised rim 318 and the second raised rim 320. An inner portion of the sloped face 328 defines the basal edge feature 116 (i.e. , the chamfered edge) of the fracture fixation plate 100.

[0174] The first raised rim 318 and the second raised rim 320 reduce a height of the cavity 311 . The narrowed annular portion of the cavity 311 between an outer portion of the sloped face 328 and the top face 324 defines a thin lip 330 which extends around a perimeter of the fracture fixation plate precursor 312. In other examples, the second raised rim 320 may include a top face which projects outwardly from the sloped face 328. In such examples, the lip 330 may be formed between the opposing top faces of the first raised rim 318 and the second raised rim 320.

[0175] As shown in FIG. 5B, the third contact face 333 defines a terminal surface of the lip of the fracture fixation plate precursor.

[0176] Where the charge includes a plurality of plies, only a some of the plies may be configured to extend into the lip 330. For example, the plurality of plies may include: net feature plies; and lip plies which are configured to project into a portion of the cavity 311 defining the lip 330.

[0177] The net feature plies may be configured to contact the first contact face 308 or the second contact face 309 along a perimeter of the plies. The lip plies may be configured to contact the third contact face 333 along a perimeter of the plies. Alternately, the lip plies may be sized to extend only partially into the portion of the cavity 311 defining the lip 330.

[0178] Providing net feature plies may ensure the resultant fracture fixation plate precursor 312 has uniform material distribution even in the extremities of the edge features 114, 116. For example, where fibre reinforced plies are used, providing net feature plies may ensure that the fibres extend along a full breadth of the edge features 114, 116. As the edge features 114, 116 form part of the final fracture fixation plate 100, the use of net feature plies ensures uniform material distribution across the final component.

[0179] In some existing compression moulding methods such as net-shape moulding, the cavity is shaped as an exact negative of the final fracture fixation plate shape so no post-moulding machining is required. In these cases, all of the plies are net-feature plies. Without an area into which the charge can overflow, compression may be incomplete resulting in defects, such as voids, which impact the surface finish and may require further post-processing.

[0180] In contrast, the cavity 311 of the novel compression moulding tool 300 is configured to define a lip 330 of the fracture fixation plate precursor 312. This lip 330 does not form part of the final fracture fixation plate 100 and is removed during postmoulding machining. The cavity is loaded with net feature plies and lip plies which are undersized (i.e., they do not extend to contact the limits of the cavity 311 when the compression moulding tool 300 is assembled). When the compression moulding tool 300 is compressed, any excess charge due to charge tolerances is able to re-distribute within the cavity 311. Any defects are localised in the lip 330 which is then removed during machining.

[0181] FIG. 6 shows the fracture fixation plate precursor 312 produced using the novel compression moulding tool 300, before any machining has taken place.

[0182] The lip 330 extends around a perimeter of the fracture fixation plate precursor 312. In this example, the lip 330 is located between the top edge feature 114 and the basal edge feature 116. The lip 330 extends outbound of the top edge feature 114 and the basal edge feature 116 to form a radially projecting flange.

[0183] As shown, the fracture fixation plate precursor 312 formed by the novel compression moulding tool 300 has final edge features 114, 116, of the fracture fixation plate 100. This contrasts to the fracture fixation plate precursor 212 of FIG. 3 which has sharp edges 214 instead of final edge features 114, 116, of the fracture fixation plate 100. The top edge features 114 and basal edge feature 116 are moulded edge features, and the lip 330 can be removed to provide the fracture fixation plate 100.

[0184] Beneficially, the fracture fixation plate precursor 312 produced using the novel compression moulding tool 300 requires less complex machining to produce the final fracture fixation plate 100. As the top edge feature 114 and the basal edge feature 116 are formed during compression moulding, these features do not need to be machined into the fracture fixation plate precursor 312.

[0185] This is best illustrated in FIG. 7 which shows the fracture fixation plate precursor 312 formed by the compression moulding tool 300 alongside the finished fracture fixation plate 100 (post machining).

[0186] A composite image 400 is provided on the right hand side of FIG. 3, which illustrates the profile of the fracture fixation plate precursor 312 overlaid onto the profileof the fracture fixation plate 100. As shown, the fracture fixation plate precursor 312 is partially oversized relative to the desired shape of the final fracture fixation plate 100.

[0187] As the edge features 114, 116, are formed by the compression moulding tool 300, these features do not need to be machined into the fracture fixation plate precursor 312 after moulding. This has several benefits over existing methods where the edge features 114, 116 are milled into the precursor during machining.

[0188] For example, moulding the top edge feature 114 has several benefits over milling the top edge feature 114 into the precursor during machining. Milling the top edge feature 114 would require the use of either a ball nose cutter, which would scan the profile, or a radius tool which would match the form of the radius. Use of either milling tool would add significant time to the machining process. For example, in the case of a ball nose cutter, several high accuracy passes would be required to form the radius shape. Even after several high accuracy passes, at a microscopic scale the edge would not be a true radius, but rather just several passes of a spherical cutter.

[0189] In the case of using a radius tool, this may be faster than a ball nose cutter, but still represents an additional stage of machining not required in the novel method of manufacture discussed herein. Additionally, depending on the desired radius geometry, milling using a radius tool would likely require a bespoke radius mill tool. This would further add to the cost of manufacture. Using a radius tool may also limit design freedom as only a constant radius edge could be achieved using such a tool.

[0190] In the novel method of manufacture, the machining stage involves removing the lip 330 from the fracture fixation plate precursor 312. In examples where the side surface 110 is parallel to the thickness direction of the fracture fixation plate precursor 312, the lip 330 may be removed by two-axis machining. For example, the lip 330 may be removed using a cutting bit aligned to cut parallel to the thickness direction of the fracture fixation plate precursor 312.

[0191] As previously discussed, for conventional methods of manufacture, variation in the thickness of the fracture fixation plate precursors can lead to inconsistency in the final shape of the fracture fixation plate. This issue is circumvented by the novel method of manufacture as the edge features 114, 116 are formed during moulding. Removal of the lip 330 is largely unaffected by the thickness of the fracture fixation plate precursor 312. As a result, the fracture fixation plates 100 produced according to the presentdisclosure may have a more consistent shape than those produced by traditional methods.

[0192] In addition, the provision of the lip 330 ensures that any defects such as voids, caused by small variation in the size / shape of the charge, are machined away and do not form part of the final fracture fixation plate 100. This represents an advantage of the novel method over existing net-shape moulding techniques. Additionally, where the plies are fibre-composite plies, the lip 330 accounts for tolerances in the cut profile of the plies. I.e., Removing the lip 330 will ensure fibres extend across the whole fracture fixation plate 100 even where the lip plies of the fracture fixation plate precursor 312 did not extend the limits of the lip 330. This represents a further benefit over net-shape moulding where the moulded piece is not oversized and so plies must be machined extremely accurately to ensure the fibres extend across the whole of the piece.

[0193] As discussed above, the novel manufacturing method of the present disclosure has several advantages over the existing methods for manufacturing fracture fixation plates. For example, the machining stage is less complex than the existing process where multiple edge features are machined. Beneficially, this may improve the speed and reduce the associated cost of producing each fracture fixation plate. As such, the production cost per fracture fixation plate may be minimised while preserving precise shape of the edge features required for the design requirements of the application.

Claims

CLAIMS1. A method of manufacturing a fracture fixation plate for stabilising a bone fracture, comprising inserting a charge into a cavity of a compression moulding tool; applying pressure to the charge within the cavity to alter a shape of the charge to form a fracture fixation plate precursor, wherein the cavity of the compression moulding tool is shaped to mould: one or more edge features of the fracture fixation plate; and a lip which projects outward beyond the one or more edge features and extends at least partially around a perimeter of the fracture fixation plate precursor; and removing the lip from the fracture fixation plate precursor to form the fracture fixation plate.

2. The method of claim 1 , wherein the one or more edge features each extend around the perimeter of the fracture fixation plate precursor.

3. The method of claim 1 , wherein the one or more edge features comprise any one or combination of: a rounded edge; a fillet radius; a chamfered edge, a bevelled edge, and a break-edge.

4. The method of any one of claims 1 to 3, wherein the one or more edge features comprises a top edge feature and a basal edge feature, and wherein the lip is located between the top edge feature and the basal edge feature.

5. The method of claim 4, wherein the fracture fixation plate precursor comprises a basal surface for engaging the bone and a top surface opposite the basal surface, and wherein removing the lip from the fracture fixation plate precursor forms a side surface of the fracture fixation plate which extends between the top surface and the basal surface, wherein the top edge feature defines a boundary between the top surface and the side surface, and wherein the basal edge feature defines a boundary between the basal surface and the side surface.

6. The method of any one of claims 1 to 5, wherein removing the lip from the fracture fixation plate precursor consists of machining the fracture fixation plate precursor.

7. The method of any one of claims 1 to 6, wherein the charge comprises a plurality of plies such as composite plies, for example carbon fibre plies.

8. The method of claim 7, wherein the charge comprises: net feature plies sized and shaped to form the one or more moulded edge features; and lip plies which are configured to project into a portion of the cavity that forms the lip.

9. The method of any one of claims 1 to 8, wherein the charge comprises polyetheretherketone.

10. A fracture fixation plate precursor for a fracture fixation plate for stabilising a bone fracture, the fracture fixation plate precursor comprising: one or more moulded edge features of the fracture fixation plate; and a lip which projects outward beyond the one or more edge features and extends at least partially around a perimeter of the fracture fixation plate precursor.11 . The fracture fixation plate precursor of claim 10, wherein the one or more moulded edge features comprise any one or combination of: a rounded edge; a fillet radius; a chamfered edge, a bevelled edge, and a break-edge.

12. The fracture fixation plate precursor of claim 10 or 11 , wherein the lip extends about the entire perimeter of the fracture fixation plate precursor.

13. The fracture fixation plate precursor of any one of claims 10 to 12, wherein the fracture fixation plate precursor comprises polyetheretherketone and reinforcement fibres, for example carbon fibres.

14. A fracture fixation plate for stabilising a bone fracture, the fracture fixation plate comprising: one or more moulded edge features; and a machined side surface adjoining the one or more edge features and extending around a perimeter of the fracture fixation plate precursor.

15. A compression moulding tool for forming a fracture fixation plate precursor, comprising at least two tool parts which together form a cavity defining a negative shape of the fracture fixation plate precursor, wherein the cavity of the compression moulding tool is shaped to mould: one or more edge features of the fracture fixation plate; and a lip which projects outward beyond the one or more edge features and extends at least partially around a perimeter of the fracture fixation plate precursor.

Images